package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.CACHE_SHOP_KEY;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Override
    public Result queryById(Long id) {
        //缓存穿透
        //Shop shop = queryWithPassThrough(id);
        //互斥锁解决缓存击穿
        //Shop shop = queryWithMutex(id);
        //逻辑过期解决缓存击穿
        Shop shop = queryWithLogicalExpire(id);
        if (shop == null){
            return Result.fail("店铺不存在");
        }
        //7.返回
        return Result.ok(shop);
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    //这个方法在redis为空的时候没办法向redis中添加缓存，所以需要先对redis进行预热或者再重新修改逻辑
    public Shop queryWithLogicalExpire(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)){
            //3.不存在，直接返回
            return null;
        }
        //4.命中，需要把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(),Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())){
            //未过期，直接返回店铺信息
            return shop;
        }
        //获取互斥锁
        String lockkey = "lock:shop:" + id;
        boolean isLock = tryLock(lockkey);
        if (isLock){
            //  开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    this.saveShopToRedis(id,30L);
                }catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockkey);
                }

            });
        }
        //返回过期的商城信息
        //7.返回
        return shop;
    }

    public Shop queryWithMutex(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)){
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中是否是空值
        if (shopJson != null){
            //返回错误信息
            return null;
        }
        //4.实现缓存重建
        //4.1获取互斥锁
        String lockkey = "lock:shop:" + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockkey);
            //4.2判断是否获取成功
            if (!isLock){
                //4.3失败，则休眠并重试
                Thread.sleep(50);
                return  queryWithMutex(id);
            }
            //4.4成功，根据id查询
            //不存在，根据id查询数据库
            shop = getById(id);
            //5.不存在，返回错误（为了解决缓存穿透问题，可以在redis上存放一个数值为null键值为该id的数据）
            if (shop == null){
                stringRedisTemplate.opsForValue().set(key, "",2L, TimeUnit.MINUTES);
                return null;
            }
            //6.存在，写入redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),30L, TimeUnit.MINUTES);
        }catch (InterruptedException e){
            throw new RuntimeException(e);
        }finally {
            //7.释放互斥锁
            unLock(lockkey);
        }
        //8.返回
        return shop;
    }

    public Shop queryWithPassThrough(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)){
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中是否是空值
        if (shopJson != null){
            //返回错误信息
            return null;
        }
        //4.不存在，根据id查询数据库
        Shop shop = getById(id);
        //5.不存在，返回错误（为了解决缓存穿透问题，可以在redis上存放一个数值为null键值为该id的数据）
        if (shop == null){
            stringRedisTemplate.opsForValue().set(key, "",2L, TimeUnit.MINUTES);
            return null;
        }
        //6.存在，写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),30L, TimeUnit.MINUTES);
        //7.返回
        return shop;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10L, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }

    private void saveShopToRedis(Long id,Long expireSeconds){
        //1.查询店铺数据
        Shop shop = getById(id);
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3.写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null){
            return Result.fail("店铺id不能为空");
        }
        //1.更新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);
        return Result.ok();
    }
}
